Corrupt external hard drive

If you are booting from the LaCie external drive, then you need to boot into Recovery Mode (Command + R) or Internet Recovery Mode (Command + Option + R) to run Disk Utility First Aid again. If Disk Utility is unable to repair the drive, then you may need to back everything up and erase the whole physical drive before reinstalling macOS or restoring from a backup. There is also a possibility your drive could be failing.

Macsupport001 Said:

“Corrupt external hard drive: I have a damaged hard drive.[...]”

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Hold It!!! — Recover this Data!

Why risk lost data? Rather than erasing the hard drive. Take this into your local AASP (Apple Authorized Service Provider). See what services they have to offer.

Go Here: Find Locations - Apple Authorized Reseller. Click: Service & Support > Enter your location information, and see if there is an AASP nearby. Contact one that shows up to find out more about the services that they offer to fix this.

Migration Assistant:

Likely, they’d go about using Migration Assistant. See if recovering this hard drive’s data is a possibility of a service they offer. If so, an AASP might do so, and then would use Migration Assistant to move forward with this and transfer it all over. Go Here: Migration Assistant - Apple Support